For pt.CXXXVII see ibid., vol.B35, p.2384 (1979). LiNO 3.3H 2O has been studied by neutron diffraction at 120 and 295 K. The final R(w.F 2) values are 4.5% (120K) and 4.9% (295K). The crystal structure found in a previous room-temperature X-ray study is confirmed: one water molecule is involved in six hydrogen bonds; the other independent water molecule in the structure has a tetrahedral environment comprising two Li + ions and two medium-strong hydrogen bonds. The four different O...O hydrogen-bond lengths increase by 0.02-0.03 Aring going from 120 to 295K. The mean-square amplitudes of vibration for the N and O atoms are found to be closely proportional to temperature. For the H and Li atoms the vibrational amplitudes are less sensitive to temperature. Crystal data: space group Cmcm, Z=4; at 120K a=6.713 (7), b=12.669 (4), c=5.968 (5) Aring; at 295K a=6.8018 (4), b=12.7132 (9), c=5.9990 (4) Aring.